Baseball historians have claimed that Foster was the best black pitcher in the early 1900s, and he would later serve as a manager, most notably for the Chicago American Giants, a team he also owned. In 1920, along with six other owners formed the Negro Leagues, with Foster as its president.

While Foster had been accused of favoring his own team in league decisions, his work was instrumental in keeping the Negro Leagues viable. By the late 1920s, Foster struggled mentally, suffering from delusions, and would literally lose his sanity. He died in 1930.

In 1981, Foster became the first executive inducted to the Baseball Hall of Fame.